Submerged tunnel bridge

ABSTRACT

A submerged tunnel bridge with positive buoyancy is anchored to the sea bottom. The bridge comprises spaced anchoring pontoons anchored to the sea bottom and operative to provide sufficient buoyancy for the submerged tunnel bridge, and bridge sections in the shape of tube-shaped tunnel sections mounted between the anchoring pontoons, the tunnel sections having such weight and buoyancy that net vertical force on the tunnel bridge sections with varying internal and external loads will vary in a range around zero.

United States Patent [191 Arild et a l.

[451 Nov. 26, 1974 1 SUBMERGED TUNNEL BRIDGE [75] Inventors; ArnulfArild, Sandvika; John Creed,

Ski; Olav Folkestad, Stabekk; Erik Odegard, Lillehammer; AntonBrandtzaeg, Trondheim; Arne Brigt Bru Selberg, Trondheim; Nils Tangsrud,Trondheim, all of Norway [73] Assignee: Norconsu1tA.S., Hovik, Norway[22] Filed: Apr. 3, 1972 21 Appl. No.: 240,722

[30] Foreign Application Priority Data Apr. 2, 1971 Norway 1261/71 [52]US. Cl. 14/27, 61/42 [51] Int. Cl E01d 15/14 [58] Field of Search 14/1,27, 18; 61/42, 72.3 [56] References Cited UNITED STATES PATENTS 11,4678/1854 Baldwin 14/1 131,322 9/1872 Anderson.'..... 262,524 8/1882Williams 447,735 3/1891 Moeser 1,852,338 4/1932 Shaffer 2,085,156 6/1937Hill 14/27 OTHER PUBLICATIONS Oceanology International 72, March, 1972;pgs. 186-190.

Primary Examiner-Nile C. Byers, Jr. Attorney, Agent, or FirmWenderoth,Lind & Ponack [5 7 ABSTRACT A submerged tunnel bridge with positivebuoyancy is anchored to the sea bottom. The bridge comprises spacedanchoring pontoons anchored to the sea bottom and operative to providesufficient buoyancy for the submerged tunnel bridge, and bridge sectionsin the shape of tube-shaped tunnel sections mounted between theanchoring pontoons, the tunnel sections having such weight. and buoyancythat net vertical force on the tunnel bridge sections with varyinginternal and external loads will vary in a range around zero.

7 Claims, '4 Drawing Figures SUBMERGED TUNNEL BRIDGE BACKGROUND OF THEINVENTION The concept of the submerged tunnel bridge is not I new.British Pat. No. 9558 Swedish Pat. No. 2095, both from 1886, andNorwegian Pat. No. 40 956 from 1924, relate to submerged tunnel bridges.In 1970 a submerged tunnel bridge was proposed as the best solution fora trafficable connection across the Strait of Messina from Sicily to theItalian mainland.

The chief advantages of a submerged tunnel bridge are partly that it canbe positioned at a depth such that it cannot hinder navigation andpartly that under certain conditions, it can be cheaper than eitherbridges or tunnels on or beneath the sea bottom.

Hitherto, however, no submerged tunnel bridges have been built,presumably because the construction and the erection problems for suchbridges have been viewed as prohibitive, for instance transverseanchoring and bridge section joining pose special problems. An attemptto solve the problem of achieving lateral stability is described inNorwegian Pat. No. 120 994,

' wherein the entrance design comprises dividing a duallane roadway intotwo separate lanes which are anchored to a rigid abutment, thus givingthe necessary transverse stability. In other proposals, transversestability is attained by inclined restraining anchorings evenlydistributed along the submerged part of the tunnel bridge. A majorproblem with this system is that both during and subsequent to theerection of the SUMMARY OF THE INVENTION The present invention solvesthe stability, anchoring I and erection problems through providing mostor all of the buoyancy necessary for the bridge with submergedcylindrical anchoring pontoons, the intervening bridge sections betweensuccessive pontoons having substantially zero net buoyancy. A furtherfeature of the invention is that the submerged anchoring pontoons haveprovisions for adjustment and tensioning of the anchor cables, which areanchor chain or wire rope. Hence the anchoring pontoons are fixed bothvertically and laterally and thereby form stable points for erecting thetunnel bridge by joining together tunnel sections. The fixing of theanchoring pontoons to the tunnel sections maybe carried out prior to orsubsequent to the submersion of the bridge. The anchoring pontoons haveadequate space for other equipment such as pumps, emergency equipment,etc.

The tube sections of the bridge are thus designed and built such thatthe weight of the sections substantially corresponds to their buoyancyin submerged position, such that their submerged weights will beapproximately equal to zero, preferably with a small residual buoyancy.Furthermore, the buoyancy of the anchoring pontoon shall be sufficientlylarge to sustain the main weight of the external and internal loads onthe tunnel section. External loads shall be understood to include forcesdue to water currents, varying salinity, growth on the outside of thetunnel sections, etc. Internal loads shall be understood as the loadsdue to the traffic, that is, the weight of the vehicles, and themovement of the vehicles through the bridge. In many cases one anchoringpontoon at each end of the tunnel section will be sufficient. In othercases it may be necessary to have several anchoring pontoons, and/or toprovide anchorings in addition to the pontoon anchorings, for instanceatthe center of a tube section, in cases where particularly largecurrent loads are anticipated.

Bridge erection is not restricted to its being divided into equal lengthspans. Within reasonable limits, the pontoons and their anchorings maybe positioned at the most suitable locations along the sea bed.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment for a bridge or a bridgesystem in accordance with the invention is schematically illustrated inthe attached drawings, wherein:

FIG. 1 comprises a lateral view of a completed submerged bridge inaccordance with the invention, the bridge crossing a fjord or thelike.

FIG. 2 comprises a plan view of the bridge shown in FIG. 1 (water notshown).

FIG. 3 comprises a schematic cross-sectional view in the transverseplane IIIIII of FIG. 1.

FIG. 4 comprises a cross-section through the bridge system in the planesII--II of FIG. 2, the left part showing a central cross-section throughthe anchoring pontoon in order further to illustratethe design of thesame.

DETAILED DESCRIPTION OF THE INVENTION Part designation numbers are thesame in all four figures: Number 2 designates the sea bed across achannel, fjord or the like, having a water surface-7; 4 and '6 designateanchor cables anchored to the sea bottom at 8 and 10, and to theanchoring pontoons 12 at a typical incline angle of 60 as shown in FIG.3. A large number of cables are used to ensure dependable and stableanchoring of each pontoon, the separate cables in each anchor groupbeing parallel with a mutual spacing such as shown in FIG. 3. Eachanchoring pontoon in the embodiment shown is cylindrically shaped andhas curved end heads 14. For example, the illustrated bridge comprisestwo anchoring pontoons 12,12, between which extends one rigid tubesection 16, having a circular cross-section as shown in FIG. 4. The tubesections are preferably cast in reinforced, pre-stressed concrete andare provided with a trafficable floor 18 and a ceiling 17 with space forventilation channels. Each end of tube section 16 is attached to itsrespective anchoring pontoon in a suitable fashion. As shown in FIG. 4,anchoring cables 4, 6 are led into the internal space of the anchoringpontoon via guides 20 in the bottom part of the pontoon. Each of thecables are fastened to an anchor 23 via adjustmentand tensioning device24. The anchoring pontoon 12 is, as shown, provided with a level floor26 for installations such as pumps and other auxiliary equipment (notshown).

Until the bridge tube section and the anchoring pontoons have beenfinally assembled, all openings are temporarily closed. Similar bridgetube sections 21 are bridge is connected to a land tunnel 22 at a levelwell below the lowest water level 7, the land connection may, however,be positioned at the depth most suitable to the incline of the slope.The bridge sectionalizing shown is symmetrical, but this choice isoptional and dependent upon local conditions. The load distributions ineach of the anchoring cables are controlled by means of tensioning meansprovided in each of the anchoring pontoons.

It will be understood that the specific design parameters forconstructing a submerged tunnel bridge in accordance with the presentinvention will vary with each specific project and location.Specifically, one skilled in the art, upon being given a contract tobuild a submerged tunnel bridge in accordance with the present inventionacross a specific body of water between two specific locations will ofcourse have to design the actual construction and dimensions of suchindividual bridge. For instance, it will of course be necessary for theproject engineer to design length of the bridge. It will also of coursebe necessary to determine the size of the tunnel bridge sections toaccommodate the anticipated traffic through the bridge. Furthermore, theproject engineer will have to determine the desired depth of the tunnelbridge dependent upon the type of shipping passing through the body ofwater and dependent upon the specific currents and type and frequency ofstorms to which the specific body of water is subjected. These factorswill of course be influential upon the design of the buoyancy of thepontoon sections and tunnel bridge sections, and also upon the size andstrength of the anchoring cables.

As stated above, each of these specific design parameters, as well asother design parameters, will be different for each individual project.However, one ordinarily skilled in this particular art would readilyunderstand how to design and construct a tunnel bridge in accordancewith the present invention, and the specific design parameters would bereadily determinable by such ordinarily skilled person.

What is claimed is:

l. A submerged tunnel bridge of the type extending from opposite landconnections across a body of water below the surface thereof, saidtunnel bridge comprismg:

at least one buoyant anchoring pontoon positioned at a predeterminedposition below said surface of said body of water;'

tube-shaped tunnel bridge sections positioned at said predeterminedposition and connected between adjacent of said anchoring pontoons andto said opposite land connections; anchoring means connected to saidanchoring pontoons and to the bottom of said body of water forsubmerging and maintaining said anchoring pontoons and said tunnelbridge sections at said predetermined position below said surface ofsaid body of water; the net buoyancy of said tunnel bridge sections atsaid predetermined position being approximately zero; and i the buoyancyof said anchoring pontoons at said predetermined position beingsufficient to sustain the weight of internal and external loads impartedto said tunnel bridge sections.

2. A submerged tunnel bridge as claimed in claim 1, wherein a portion ofthe internal space of said tunnel bridge sections constitutes a portionof the buoyancy space of said anchoring pontoons.

3. A submerged tunnel bridge as claimed in claim 1, wherein each of saidanchoring pontoons is in the form of a cylinder, the longitudinal axisof which is transverse to the longitudinal axes of the adjacent of saidtunnel bridge sections; and wherein said adjacent tunnel bridge sectionsare connected to opposite sides of said cylinder.

4. A submerged tunnel bridge as claimed in claim 1, wherein saidopposite land connections are positioned below said surface of said bodyof water, the connection between said land connections and said tunnelbridge sections thus being below said surface of said body of water, thebuoyancy of said tunnel bridge sections connected to said landconnections thus being constant.

5. A submerged tunnel bridge as claimed in claim 1, wherein each of saidanchoring pontoons has a buoyancy space partially defined by an upperwall and a lower wall; and said anchoring means comprise cablesextending through said lower wall of each of said anchoring pontoons andfixed to said upper wall thereof.

6. A submerged tunnel bridge as claimed in claim 5, further comprisingadjusting and tensioning means attached to each of said cables andpositioned within said buoyancy space of each of said anchoringpontoons.

7. A submerged tunnel bridge as claimed in claim 1, wherein said netbuoyancy of said tunnel bridge sections is slightly positive, suchpositive buoyancy being sufficient to sustain the weight of saidinternal loads.

1. A submerged tunnel bridge of the type extending from opposite landconnections across a body of water below the surface thereof, saidtunnel bridge comprising: at least one buoyant anchoring pontoonpositioned at a predetermined position below said surface of said bodyof water; tube-shaped tunnel bridge sections positioned at saidpredetermined position and connected between adjacent of said anchoringpontoons and to said opposite land connections; anchoring meansconnected to said anchoring pontoons and to the bottom of said body ofwater for submerging and maintaining said anchoring pontoons and saidtunnel bridge sections at said predetermined position below said surfaceof said body of water; the net buoyancy of said tunnel bridge sectionsat said predetermined position being approximately zero; and thebuoyancy of said anchoring pontoons at said predetermined position beingsufficient to sustain the weight of internal and external loads impartedto said tunnel bridge sections.
 2. A submerged tunnel bridge as claimedin claim 1, wherein a portion of the internal space of said tunnelbridge sections constitutes a portion of the buoyancy space of saidanchoring pontoons.
 3. A submerged tunnel bridge as claimed in claim 1,wherein each of said anchoring pontoons is in the form of a cylinder,the longitudinal axis of which is transverse to the longitudinal axes ofthe adjacent of said tunnel bridge sections; and wherein said adjacenttunnel bridge sections are connected to opposite sides of said cylinder.4. A submerged tunnel bridge as claimed in claim 1, wherein saidopposite land connections are positioned below said surface of said bodyof water, the connection between said land connections and said tunnelbridge sections thus being below said surface of said body of water, thebuoyancy of said tunnel bridge sections connected to said landconnections thus being constant.
 5. A submerged tunnel bridge as claimedin claim 1, wherein each of said anchoring pontoons has a buoyancy spacepartially defined by an upper wall and a lower wall; and said anchoringmeans comprise cables extending through said lower wall of each of saidanchoring pontoons and fixed to said upper wall thereof.
 6. A submergedtunnel bridge as claimed in claim 5, further comprising adjusting andtensioning means attached to each of said cables and positioned withinsaid buoyancy space of each of said anchoring pontoons.
 7. A submergedtunnel bridge as claimed in claim 1, wherein said net buoyancy of saidtunnel bridge sections is slightly positive, such positive buoyancybeing sufficient to sustain the weight of said internal loads.